فصلنامه جنگل و فرآورده های چوب
سال هفتاد و ششم شماره 4 (زمستان 1402)

The purpose of this research is to evaluate and compare the effects of two native and non-native species of Prosopis (Prosopis cineraria and P. juliflora) on the physical, chemical, and biological characteristics of soil in Sistan and Baluchistan province in Iran. For sampling, 30 trees from each species were selected, and soil samples were taken from a depth of 0-30 cm both under and outside their canopy. After combining all 5 soil samples for each species, samples were obtained for laboratory analysis. Soil properties such as saturated moisture (SM), pH, electrical conductivity (EC), organic carbon (OC), total nitrogen (TN), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), microbial respiration (SMR), substrate-induced respiration (SIR), microbial biomass carbon (MBC), nitrification potential (PN), as well as urease, dehydrogenase, alkaline phosphatase, and acid phosphatase enzyme activity were measured in the laboratory. Based on these measurements, a soil quality index was calculated. The results significantly showed that the highest values of SM, TN, SIR, and dehydrogenase enzyme were found under the canopy of P. cineraria, while the highest values of Mg, P, TN, and acid phosphatase enzymes were observed under the canopy of P. juliflora species. The lowest values of these parameters were observed outside the canopy of both species. The soil quality index indicates that soil quality under the P. cineraria tree is higher than under the P. juliflora tree and outside the crown canopy of both species. The conclusion suggests that native Prosopis tree species improve soil fertility and acidity, with soil quality under their canopy being numerically higher than under non-native Prosopis. Therefore, preserving natural forests of P. cineraria species and afforestation with it are recommended to maintain and improve soil quality in Sistan and Baluchestan province.

In recent decades, the use of environmentally friendly insecticides, especially plant essential oils (EO), has attracted the attention of many researchers. The aim of this study was to investigate the insecticidal effects of essential oils extracted from Juniperus excelsa needles collected from Aqdagh (Khalkhal) and Shahrestanak (Karaj) in Iran against adults of Plodia interpunctella and Tenebrio molitor. The essential oil was extracted from the needles of the plant using the clevenger apparatus, and the compounds were analyzed using a gas chromatograph coupled with a mass spectrometer (GC-MS). Fumigant toxicity of the EO was also evaluated against the above-mentioned insects by probit regression and the LC50 index. Based on the results, the chemical compounds identified in the EO from Shahrestanak and Aqdagh regions were 24 and 18 compounds, respectively. However, α-pinene was the main component of the EOs obtained from both habitats. Additionally, the results showed that the respiratory toxicity of EO in both studied areas had a positive and significant correlation with the concentration of essential oils (p < 0.01). Therefore, it seems that the EO extracted from J. excelsa needles has a high potential for use in pest control programs in warehouses. The calculated LC50 indices of Aqdagh and Shahrestank essential oils for Tenebrio molitor was 279.10 and 253.16 µl/L, respectively. Also, the indices of Aqdagh and Shahrestank essential oils for P. interpunctella were 182.26 and 115.16 µl/L, respectively. The LC50 values of Shahrestank EO were lower for both insects, probably due to the difference in the chemical compositions of Aqdagh and Shahrestanak essential oils. Considering the respiratory toxicity of the essential oil obtained from juniper leaves in two regions, and considering the difference in LC50 index, more biometric studies of J. excelsa in different habitats are recommended.

This research was designed to investigate the dieback of oak (Quercus infectoria; Q. libani) trees in the northern Zagros forests in West Azerbaijan Province. Characteristics of the stand were investigated in a one-hectare sample plot with dimensions of 100 × 100 meters. To monitor dieback, inside the sample, a sub-plot with a floating surface was determined where 100 oak trees could be placed. The dieback was monitored over four years (2019-2022) using a five-level scale: 1) healthy, 2) dieback, 3) crown dieback up to 50%, 4) crown dieback exceeding 50%, and 5) tree cut down. The results showed a decrease in the number of healthy trees from 94% to 71% between 2019 and 2022, with 9% of trees ultimately being cut down. To investigate the relationship between leaf surface and the dimensions and weight of seeds of trees, 20 leaves were selected from five permanent trees, and their surface was calculated annually for three years (2019-2021). Additionally, 25 seeds were harvested, and the dimensions and weight of the seeds were determined annually. The results of calculating the average leaf area over three years showed a significant decreasing trend. Except for seed weight, other dimensions in the seed showed a significant decreasing trend during the monitoring years. Overall, the results showed that despite the absence of oak charcoal disease in the province, the trend of decreasing healthy trees and increasing trees with different levels of dieback is very worrying.

This research was conducted to enhance the strength and reduce the water absorption of gypsum board. Initially, the effect of unbleached fiber was examined, followed by an investigation into the impact of calcium carbonate modified with stearic acid, lignosulfonate, polyvinyl alcohol, corn starch, and tapioca on the flexural strength of the samples. These additives were incorporated into the plaster at varying levels to determine the most effective amount for improving the properties of the gypsum board, including bending strength, through trial and error. The compressive strength, water absorption, density, and microstructure of samples from optimal treatments were analyzed. The results revealed that stearic acid formed a coating layer on the calcium carbonate particles, reducing moisture absorption to approximately 1.1 times that of untreated fibers compared to the control samples. Furthermore, the compressive strength increased in all treatments with unbleached pulp compared to the control samples, with tapioca starch showing the most significant increase at 2.3 times that of the control samples. Electron microscope images displayed a uniform distribution of gypsum fibers and crystals, resulting in a homogeneous texture and proper connection between them. Despite falling into the low-density category (0.74 g/cm3), the optimal treatment samples exhibited higher compressive strength than the minimum standard value. The produced gypsum boards demonstrated standard resistance and appropriate water absorption.

The Zagros forests are known as the second-largest forest ecosystems in the country in terms of surface area, and they provide many ecosystem services such as carbon storage. Soils are the largest reservoir of carbon storage in dry ecosystems. The purpose of this study was to investigate the carbon storage status of coppice oak stands (exclosure and non-protected stands). In this regard, two forest stands, Garan (an exclosure area) and Dolah Naw (a typical forest of Kurdistan province), were selected in Marivan county, Kurdistan province. A square sample plot of one hectare was considered randomly in each stand. In each plot, five soil samples were taken from a depth of 0-30 cm, and physico-chemical characteristics of the soil, microbial respiration, and organic carbon percentage were measured in the laboratory. Considering the normality of the data, the independent t-test was used to compare the averages of the study parameters in the two plots. The results showed that the percentage of organic carbon and carbon storage in the Garan, with values of 3.63% and 104.3 tons per hectare, respectively, was significantly higher than that of the Dolah Naw (with 2.63% and 86.7 tons per hectare). Additionally, the parameter values of gravel percentage, microbial respiration, and C/N ratio in the Garan (37.3%, 472.9 mg CO2/kg, and 13.1, respectively) were higher than those in the Dolah Naw. The general results of the research showed that carbon storage in the Garan stand (under protection management) exceeded that of the Dolah Naw. As a result, exclosure and forest protection increases the percentage of carbon storage and the amount of soil carbon storage.

The occurrence of log damage happens at different stages of logging, but minimizing it is one of the principles of proper logging. The purpose of this study was to estimate the wood volume losses during the harvesting stages of garden trees in Langaroud County. In order to calculate the wood value loss following tree felling, the selection sampling method was used. In total, 52 trees consisting of oak (Quercus castaneifolia C.A. Mey), Caucasian wingnut (Petrocarya fraxinifolia (Lam.) Spach), alder (Alnus glutinosa L.), elm (Ulmus carpinifolia Borkh.), and maple (Acer velutinum Boiss.) species across three diameter classes of 20-40, 40-60, and >60 cm were measured. Two-way ANOVA and Duncan tests were used to analyze the data. The results showed that the sum of wood loss rates in oak, Caucasian wingnut, alder, elm, and maple species are 0.644, 0.467, 0.610, 0.466, and 0.499 m3, respectively. Additionally, the results showed that with the increase of diameter classes, the rate of wood loss increased in all species. The results of the ANOVA test showed that there was a significant difference between the volumes of wood loss in the diameter classes, but there was no significant difference between different species. The cross impact of diameter classes and tree species on the rate of volume wood loss did not show any significant difference. The results of the Duncan test showed that there was a significant difference in volume wood loss in the tree diameter classes. The results also showed that the volume wood loss in all species (52 trees) is 2.686 m3, with a value of 148,389,000 Rials. In general, the results indicate that by reducing the wood volume loss, it is possible to increase income from cutting and selling wood products.

The performance of formaldehyde-free tannin and tannin-resorcinol-formaldehyde resins was investigated in comparison with melamine-formaldehyde resin to improve the physical and mechanical characteristics of oak wood. Melamine-formaldehyde resin was diluted to a concentration of 25% and then 5% carbamide was added to reduce its viscosity. For the synthesis of formaldehyde-free tannin resin, condensed tannin powder with a concentration of 30% in distilled water was used, and the pH was adjusted to the range of 10 using a 33% solution of sodium hydroxide in water. Tannin-resorcinol-formaldehyde resin was also synthesized at pH 8. After impregnation of the wood samples using the empty cell process and drying them with a moisture-based schedule, the resins were cured in an oven at a temperature of 103 ± 2°C for 48 hours and then at a temperature of 120°C for 4 hours. The results showed that modifying wood with all three types of resin leads to a decrease in equilibrium moisture content, improvement in dimensional stability, and surface water repellency. However, it does not have a significant effect on the hardness and modulus of elasticity of the wood. The weight percent gain after modification with melamine-formaldehyde resin (23.8%) was almost twice its value for wood modified with tannin-based resins. Melamine-formaldehyde resin had a better performance in comparison with tannin-based resins, while the intensity of wood color change after modification was also less. The modification process with tannin-resorcinol-formaldehyde resin was more successful in improving the properties compared to formaldehyde-free tannin resin.

The utilization of wood is limited due to its vulnerability to moisture, dimensional changes, and susceptibility to both living organisms and environmental factors. One method of wood enhancement involves impregnating the wood with various aminic resin monomers and subsequently converting them into polymers within the wood structure. This study aims to enhance the physical properties of poplar (Populus deltoides)  wood by employing MF resin for saturation. Additionally, a 5% boric acid solution is utilized during saturation to enhance resistance against fungal decay. The first part of the study involved saturating wood samples with different concentrations (7%, 15%, 27%, and 35%) of MF resin, using the vacuum/pressure technique, and examining the properties of the treated wood. In the second part, samples were treated with resins made at different molar ratios to investigate the impact of free formaldehyde and other additives on decay resistance. Results revealed a substantial increase in weight gain percentage as resin concentration increased during wood saturation. The impregnation of wood with MF resin and subsequent polymer formation within the wood structure, even after leaching procedure in accordance with EN 84 standard, significantly improved the samples' resistance against white rot decay. Treatment with different resin concentrations considerably enhanced pine wood's resistance to decay. Resins with higher formaldehyde ratios and the inclusion of boric acid as an additional protective measure did not significantly impact the decay resistance of the treated samples. The findings of this study underscore the considerable potential of using MF resin to boost wood's resistance against decay.